% --- \chapter{Introduction} ---
\chapter*{Acknowledgements}
\addcontentsline{toc}{chapter}{Acknowledgements}
\markboth{}{}
I wish to express my gratitude to:
\begin{itemize}
\item My thesis supervisor, {\bf Hans Olofsson}, for his wise guidance through this magnificent adventure. I will always appreciate his availability and concern for discussions.

\item My external advisor, {\bf Hugo Schwarz}, for his support during the observational runs. His broad experience at the telescopes has been crucial for the successful outcome of this thesis.

\item Collaborators, {\bf Kjell Eriksson, Bengt Gustafsson, Franz Kerschbaum \& Fredrik L. Sch\"oier}, for discussions on the papers material.

\item {\bf Ryszard Szczerba \& Tim Gledhill} for welcoming me at their home institutions and sharing some of their knowledge with me.

\item {\bf Kay Justtanont \& G\"oran Olofsson} for careful reading and smart comments on this manuscript.

\item My colleagues at the Stockholm Observatory, especially those with whom I have spent good moments. In particular, {\bf Luc Rouppe van der Voort} and {\bf Nicole von der Bliek} for the nice chats we used to have and their friendship, and {\bf Uno W\"ann} for his kindness and disposition to help.

\item My friends in Stockholm. Throughout these years a large number of people have entered my life, leaving (mainly) pleasant memories. I will always be thankful for all the moments I shared with them.

\item My family and friends on Tenerife for letting me feel that after all this time I still have a home down there.

\item Mother Nature for kindly arranging everything so that I could experience the frustration of being an observational astronomer in possession of a large telescope in a starless night.

\item Mother Nature for kindly arranging everything so that I could subsequently experience the excitation of being an observational astronomer in possession of a large telescope in a starry night.

\item My two 'pearls' that have been by my side throughout these years. Thanks so much for being there in the lowest and highest moments of my time in Sweden.
 

\end{itemize}
